How Does the Neurodevelopmental Hypothesis Explain the Difficulty of Locating

How does the neurodevelopmental hypothesis explain the difficulty of locating a gene for schizophrenia?​

A) The gene or genes for schizophrenia do not affect behavior until early adulthood.
B) ​The gene sometimes appears on one chromosome, and sometimes another.
C) ​The gene exerts its effects in different ways for different people.
D) ​Schizophrenia can result from prenatal environment instead of genetics.